For many years, fresh market leafy green vegetables periodically have become contaminated with foodborne human pathogens. Despite this on-going problem, little is known about where such pathogens come from, how they reach leafy vegetables, how they persist in farming environments, the role of post-harvest contamination, and other aspects. While many laboratory, growth chamber, and greenhouse studies provide some information on how E. coli and other pathogens might interact with leafy vegetables such as lettuce and spinach, it is notable that few in-field research projects have been used to address such issues. Our proposal has the advantage of being a practical field study conducted in the Salinas Valley in a commercially farmed crop of spinach. By inoculating replicated spinach plots with either a generic or a non-toxigenic O157:H7 strain of E. coli, we will monitor the survival of this organism under coastal California, field production conditions. With this simulation of a contamination event in spinach, we should gain a better understanding of the ecology and dynamics of E. coli in an agricultural setting. A second aspect of our proposal will examine the phenomenon of 'internalization,' which holds that a plant can absorb a human pathogen (via root uptake, for example) and transport the pathogen to leaves that will be later consumed. Researchers that feel internalization takes place have mostly dealt with leafy vegetables grown in pots under artificial conditions. In our proposal we will test commercially grown spinach to see if internalization can take place in a field setting.